Windows having double-glazed sliding glass doors have heretofore been proposed to provide good sound and heat insulating properties. However, in a window of this structure, two glazed sliding glass doors are mounted in a parallel arrangement, and therefore the width of the sash is enlarged. Further, to open a window having glazed sliding doors, each door must be separately operated beginning with the operation of the interior door.
In an attempt to overcome these difficulties, a window having sliding doors as disclosed in Japanese Patent Publication No. 43269/1978 has been proposed. Specifically, the window has an interior, double-glazed sliding door and an exterior, double-glazed door, the frames of these doors being secured with metal fixtures. Thus, this double window structure can be operated in the same way as a window having single-glazed sliding doors. Further, the doors can be supported by a single sash. In addition, since horizontal blinds are mounted within the double-glazed doors, it acts as an excellent heat, sound, and sunlight insulator.
However, in order to install the sliding doors in the sash, the four glazed glass panel assemblies are required to be mounted on their respective rails one by one and thus a cumbersome operation is necessary. Further, when the glazed interior glass panel assemblies are carried and installed in the sash after the two pairs of the glazed doors are separately fixed with metal fixtures, the total load of the glazed exterior doors is imposed only on the fixtures. Hence, the fixtures are required to be strong enough to firmly fix the two doors. Additionally, the four rails juxtaposed in the sash are inconvenient to clean.